This invention relates to the formation and construction of foam-core materials, such as may be used in the construction of such diverse items as surfboards, sailboards, home built and/or light aircraft, or any other product with a laminated foam core. A typical method of forming a surfboard uses fiberglass or other fiber-reinforced plastic laminated over a foam-core. A rigid polyester-urethane foam is carved and sanded to the desired shape, and a hard shell of fiberglass-reinforced polyester-resin is laminated over the core. Various end uses of the boards (e.g. amateur vs. professional) require varying properties of the boards, effected by the materials used in the construction. The foam core can be made from low-density urethane, styrene, or PVC foam, with any suitable laminating material such as polyester or epoxy resin with carbon, kevlar, or glass fibers.
One of the limiting factors in producing a light, yet strong, board is the strength-to-density ratio of the foam core. Although the rigid foams used in surfboards are relatively strong for their density, there are two problems that arise in the manufacture of such boards:
1. Spars (or `stringers`) are usually placed longitudinally through the core of the board, to carry the compressive and shear loads of the board during bending, because the foam core alone cannot sustain the loads; and PA1 2. Extra laminations are usually required on the deck of the boards where the feet of the rider contact the deck, because the foam core tends to fail when in compression beneath the fiberglass shell, leading to dents, delamination of fiberglass from foam, fractures in the fiberglass, and, finally, the structural degradation of the board. PA1 (a) providing an acidic mixture (e.g. isocyanic acid) that is capable of foaming a plastic resin/plastic foaming agent/catalyst; PA1 (b) providing a plastic resin/plastic foaming agent/catalyst which is capable of being foamed by the acidic mixture; PA1 (c) mixing a first portion of the acidic mixture with a first portion of the, plastic resin/plastic foaming agent/catalyst to produce a first mixture; PA1 (d) pouring simultaneously the first mixture of step (c) in a form of a first row on a generally planar surface; PA1 (e) curing the first row of step (d) to produce a first row of foamed plastic having a first shell thereof; PA1 (f) mixing a second portion of the acidic mixture with a second portion of the plastic resin/plastic foaming agent/catalyst to produce a second mixture; PA1 (g) pouring simultaneously the second mixture of step (f) in a form of a second row on the generally planar surface juxtaposed to and in contact with the first shell of step (e); PA1 (h) curing the second row of step (g) to produce a second row of foamed plastic having a second shell thereof that is bound to the first row of step (e) and comprises the second shell thereof terminating in the first shell to form a first trough between the first shell and the second shell; PA1 (i) mixing a third portion of the acidic mixture with a third portion of the plastic resin/plastic foaming agent/catalyst to produce a third mixture; PA1 (j) pouring simultaneously the third mixture of step (i) in a form of a third row in the first trough of step (h) so as to be in contact with the first shell of step (e) and the second shell of step (h); PA1 (k) curing the third row of step (j) to produce a third row of foamed plastic having a third shell thereof, the third shell being bound to the first row and to the second row, having the second shell terminating in the first shell and the third shell terminating in the second shell, and such that a vertical sectional view through the plastic foam composition of matter defines each of the first, second, and third shells as being convex. PA1 (a) mixing an acidic mixture with a plastic resin/plastic foaming agent/catalyst to produce a foaming mixture; PA1 (b) depositing a row of the foaming mixture on a generally planar surface; PA1 (c) curing the row to produce a row of foamed plastic having a shell; PA1 (d) repeating steps (a)-(c) for depositing a row contiguous to the row of step (c) such that a trough is formed therebetween; PA1 (e) repeating steps (a)-(d) for depositing a plurality of generally parallel contiguous rows until a desired number of rows is deposited such that any two contiguous rows defines a trough therebetween; and PA1 (f) repeating steps (a)-(d) to deposit rows in the troughs defined between any two contiguous rows to form a generally pyramidally shaped composition of matter generally comprising layers of contiguous rows disposed in troughs between underlying layers of contiguous rows. PA1 (a) providing a plurality of rod members having an hexagonally shaped horizontal cross section; PA1 (b) providing an adhesive; PA1 (c) disposing a portion of the adhesive on a first rod member; PA1 (d) securing a second rod member to the first rod member; and PA1 (e) repeating steps c-d for successive rod members. PA1 (a) providing a plastic that is capable of foaming, an injecting means, and glue; PA1 (b) providing a first mold comprising an first interior mold area defining a half-honeycomb shape and a second mold comprising a second interior mold area defining a half-honeycomb shape; PA1 (c) disposing the molds such that the first interior mold area and the second interior mold area form a continuous mold area which is honeycomb shaped in cross-section; PA1 (d) causing the plastic to foam; PA1 (e) injecting the foam into the continuous mold area with the injecting means; PA1 (f) curing the foam of step (e) to produce hexagonally shaped foam rod defining six hexagon sides; PA1 (g) removing the hexagonally shaped foam rod from the first mold and the second mold; PA1 (g) repeating steps (c)-(g) to produce a plurality of hexagonally shaped foam rods each having six hexagon sides; PA1 (h) gluing the plurality of hexagonally shaped rods together such that at least two of the six hexagon sides of any one of the plurality of hexagonally shaped rods are glued to at least two more of the plurality of hexagonally shaped rods to produce a plastic composition of matter defining cellular hexagonally shaped walls in vertical cross section.
The above problems add to the cost and time of fabrication of such boards. Further, such boards are typically undesirably heavier. The need for additional laminations and spars can be reduced or eliminated by increasing the strength of the foam core, particularly in resistance to compression in a vertical direction.
The above problems can be markedly reduced or eliminated by the method of the present invention. A foam or foam core having a cellular structure, such as half circular or honeycomb, inherently formed in the foam is produced by mixing a foamable plastic, such as two-part urethane foam system or any other system for producing a plastic foam such as P.V.C., placing beads or rows expressed from the foamable plastic side-by-side, curing the rows, placing another layer of side-by-side foam rows over the first layer, curing the second layer, repeating this process (i.e., to achieve as many additional rows as desired) to form a billet or board of cured foam, and cutting the billet vertically and trimming the resultant sections.
A patentability search was conducted and the following U.S. Patents were found: U.S. Pat. No. 3,514,798 to Ellis; U.S. Pat. No. 3,543,315 to Hoffman; U.S. Pat. No. 4,713,032 to Frank; U.S. Pat. No. 4,753,836 to Mizell; U.S. Pat. No. 4,797,312 to Sherwood; U.S. Pat. No. 4,961,715 to Shanelec; U.S. Pat. No. 5,023,042 to Efferding; and U.S. Pat. No. 5,234,638 to Jang.
The U.S. Pat. No. 3,514,798 to Ellis teaches a method of constructing a lighter surfboard comprising a surfboard in which the outer shell or skin is composed of solidified laminating polyester resin onto which, while the resin is still moist, is pressed a sheet of glass cloth which is then impregnated with the same resin. This occurs on the interior surface of each half of a mold having the configuration of the surf-board when mold is closed and onto this moist shell is pressed and secured thereto by adhesion a sheet of honey-comb material such as kraft liner board impregnated with a thermosetting phenolic resin.
The U.S. Pat. No. 3,543,315 to Hoffman teaches surfboard fabrication providing increased safety insofar as the usual hard surfacing thereof is virtually eliminated. Specifically, a surfboard is fabricated with a low density core contoured to the required depth and carrying spaced stress members, and over which a skin of depressible material is carried for supporting engagement of a person's body parts, for example.
The U.S. Pat. No. 4,713,032 to Frank teaches a method of making a sailboard or surfboard, in which a prefabricated foam core has fibrous material wound about it and a polyurethane resin especially set with a reaction retarder is poured onto the fibrous material, whereupon the thus treated foam core is inserted in a molding tool and the mold is closed for curing the polyurethane resin.
The U.S. Pat. No. 4,753,836 to Mizell teaches a lightweight resin/glass fiber covered article such as a surfboard. A portion of the upper surface of the article has the ability to withstand exterior surface pressure applied on a small area without damage to the surface thereof. The article has a rigid foam core to which a resilient foam cushion is adhered over which a thin rigid foam sheet is applied and the entire article is coated with a resin and glass fiber layer. The method of making the article is also disclosed.
The U.S. Pat. No. 4,797,312 to Sherwood teaches a surface-reinforced lightweight article, which includes a honeycomb structure whose sidewalls are reinforced by an expanded foam. The article can be manufactured by laying a fibrous third layer, such as several layers of dry tissue paper backed by a layer of dry fiberglass cloth, on the walls of a mold,laying a second layer of multi-cell honeycomb-like material against the third layer, and laying a finely porous first layer such as tissue paper over the second layer. Foamable plastic is poured in the mold over the three layers into a tight sandwich and permeates the layers to reinforce them. Specifically, expanded foam in the cells of multi-cell honeycomb type material braces the honeycomb sidewalls against collapse, to greatly increase the strength and rigidness of the article.
The U.S. Pat. No. 4,961,715 to Shanelec teaches surfboards and the like formed of molded foam composed of expanded polypropylene foam beads, having a density of approximately 3.75 PCF, melted together with steam pressure.
The U.S. Pat. No. 5,023,042 to Efferding teaches that sailboards having a tucked rail are made from a flexible resilient mold so that the seam of the board is along its bottom edges instead of at its point of greatest breadth. A flexible mold part having the contour of the sailboard to be produced has an opening smaller than the greatest breadth of the board. The mold is first flexed so that its opening is sufficiently wide to receive the blank that forms the body of the sailboard. Secondly, the blank is inserted into the flexed mold, and thirdly, the mold is released and its resiliency returns it to its original shape. A conventional rigid mold part closes the open end, and a vacuum is applied to form the final product. The flexible mold part is flexed a second time to remove the product.
The U.S. Pat. No. 5,234,638 to Jang teaches a surfboard making process including the steps of preparing a polyethylene bag to hold a foamed EPS (expanded polystyrene), treating the polyethylene bag with the foamed EPS through a secondary foaming process, and putting the product thus obtained from the secondary foaming process in the molding cavity of a molding die for treating into a surfboard by a steam bath.
None of the foregoing teach the particular foam or method for producing same of the present invention.